Update: Wired has an article with an amusing blurb about Google's move toward WiFi:

The little search engine that could continues evolving into a Hydra-like monster. It's newest head will chew its way into the wireless internet world, making Google a direct competitor of ISPs and telecom companies.

I'm not really sure, frankly. Google does claim they want to make information universally accessible. It could be as simple as that, making it so more people can use Google more often to find the information they want and need.